Adhesive film for display device, display device including the same, and method for manufacturing the same

ABSTRACT

A display device includes a display panel, a cover member disposed on the display panel, and an adhesive layer disposed between the display panel and the cover member. The adhesive layer has a first surface facing the cover member and a second surface facing the display panel, and includes a first area and a second area disposed at positions different from each other in a first direction from the first surface toward the second surface. A modulus of the first area is different from a modulus of the second area.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2019-0051435, filed on May 2, 2019, which is herebyincorporated by all purposes as if fully set forth herein.

BACKGROUND Field

Exemplary implementations of the invention relate generally to a layerfor display devices and, more specifically, to an adhesive film fordisplay devices, a display device including the adhesive film, and amethod for manufacturing the adhesive film for display devices.

Discussion of the Background

In recent times, liquid crystal display (LCD) devices or organic lightemitting diode (OLED) display devices may be used as a display devicefor electronic devices, e.g., mobile phones, navigation devices, digitalcameras, electronic books, portable game machines, and variousterminals.

In a conventional display device used in such electronic devices, acover window that is transparent may be provided in front of a displaypanel so that users may view a display area of the display panel. Thecover window should be strong against external impact to protect thedisplay panel in the device.

In addition, recently, studies have been actively conducted on displaydevices that may be foldable or rollable, and a cover window applied tosuch a display device includes a transparent window that is flexible tobe folded.

In such a case, an adhesive layer for attaching the cover window on thedisplay panel may be disposed between the display panel and the coverwindow.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Applicant discovered that it is preferable to use an adhesive layerhaving a relatively high modulus and a relatively high bending stiffnessto prevent a cover window from being broken when a display device isfolded or rolled. On the other hand, an adhesive layer having arelatively low modulus and a relatively low bending stiffness may bepreferable to prevent occurrence of bright spots due to an impactapplied to the display panel.

Adhesive films and display devices including adhesive films constructedaccording to the principles and exemplary implementations of theinvention and methods of manufacturing adhesive film according to theprinciples and exemplary implementations of the invention are capable ofpreventing or at least reducing a cover member from being damaged and/orbroken when a display device is folded and preventing or at leastreducing visually recognizable spots such as bright spots from occurringdue to an impact applied to the display device and/or its display panel.For example, an adhesive layer for a display device has a modulus and abending stiffness varying in a thickness and/or length direction.

An adhesive layer for a display device may include a first area having arelatively high modulus and a relatively high bending stiffness and asecond area having a relatively low modulus and a relatively low bendingstiffness. For example, the first area may include a first surface ofthe adhesive layer, and the second area may include a second surface ofthe adhesive layer opposing the first surface. The first area of theadhesive layer may prevent or at least reduce the cover member frombeing damaged and/or broken when the display device is folded, and thesecond area of the adhesive layer may prevent or at least reduce brightspots from occurring due to an impact applied to the display device. Thefirst surface may be a front surface of the adhesive layer, and thesecond surface may be a rear surface of the adhesive layer. For anotherexample, the first area may overlap a folding area of the displaydevice, and the second area may overlap a non-folding area of thedisplay device. In this case, the first area may prevent or at leastreduce buckling due to shearing forces of the adhesive layer that may begenerated when the folding area is folded, and the second area mayprevent or at least reduce bright spots from occurring due to an impactapplied to the display device.

An adhesive layer for a display device may include a single layer. Inthis manner, the manufacturing processes may be simplified, and imagequality of the display device may be improved since the single adhesivelayer may prevent or at least reduce reflection or refraction of lightthat may occur at an interface between plural layers. In addition, sincethe single adhesive layer does not easily peel off dissimilarly toplural layers, the adhesive layer and the display device may be robustto stress.

Additional features of the inventive concepts will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the inventive concepts.

According to one aspect of the invention, a display device includes: adisplay panel; a cover member disposed on the display panel; and anadhesive layer disposed between the display panel and the cover member,wherein the adhesive layer has a first surface facing the cover memberand a second surface facing the display panel, and includes a first areaand a second area disposed at positions different from each other in afirst direction from the first surface toward the second surface, andwherein a modulus of the first area is different from a modulus of thesecond area.

The adhesive layer may form a single layer including the first area andthe second area without an interface between the first surface and thesecond surface.

The adhesive layer may have a continuous modulus between the firstsurface and the second surface.

The modulus of the first area may be about 100 Kpa or higher and about1000 Kpa or lower, and the modulus of the second area may be about 100Kpa or lower.

A difference between the modulus of the first area and the modulus ofthe second area may be about 100 Kpa or greater.

The first area may include the first surface; the second area mayinclude the second surface; and the modulus of the first area may behigher than the modulus of the second area.

The first area may include the first surface; the second area mayinclude the second surface; and the modulus of the first area may belower than the modulus of the second area.

A bending stiffness of the first area may be about 30 N·cm or higher andabout 50 N·cm or lower, and a bending stiffness of the second area maybe about 15 N·cm or higher and about 30 N·cm or lower.

Each the moduli of the first and the second areas may vary graduallyalong the first direction; the first area may include the first surface;and the second area may include the second surface.

The adhesive layer may further include a third area having a modulusthat varies gradually along the first direction.

The third area may have a modulus that decreases gradually along thefirst direction.

The first area may include the first surface; the second area mayinclude the second surface; the third area may be disposed between thefirst area and the second area; and the modulus of the first area andthe modulus of the second area may be constant in the first direction.

The third area may have as a modulus that increases gradually along thefirst direction.

The first area may include a third area having a modulus that decreasesgradually along the first direction, and the second area may include afourth area having a modulus that increases gradually along the firstdirection.

The first area may include the first surface, and the second area mayinclude the second surface.

The first area may include the second surface, and the second area mayinclude the first surface.

The adhesive layer further may include a third area disposed between thefirst area and the second area, and each of the modulus of the firstarea and the modulus of the second area may be higher than a modulus ofthe third area.

The adhesive layer may further include a third area disposed between thefirst area and the second area, and each of the modulus of the firstarea and the modulus of the second area may be lower than a modulus ofthe third area.

The display device is foldable or rollable.

According to another aspect of the invention, a display device includes:a display panel; a cover member disposed on the display panel; and asingle adhesive layer including a first surface facing the cover memberand a second surface facing the display panel without an interfacebetween the first surface and the second surface, the single adhesivelayer being disposed between the display panel and the cover member,wherein a modulus of the first surface is higher than a modulus of thesecond surface.

A difference between the modulus of the first surface and the modulus ofthe second surface may be about 100 Kpa or greater.

According to still another aspect of the invention, a display deviceincludes: a display panel; a cover member disposed on the display panel;and an adhesive layer disposed between the display panel and the covermember, wherein the adhesive layer includes non-folding areas and afolding area disposed between the non-folding areas, and wherein amodulus of the folding area is greater than a modulus of the non-foldingarea.

The modulus of the folding area may be about 100 Kpa or higher and about1000 Kpa or lower, and the modulus of the non-folding area may be about100 Kpa or lower.

A difference between the modulus of the folding area and the modulus ofthe non-folding area may be about 100 Kpa or greater.

According to yet another aspect of the invention, an adhesive film for adisplay device, the adhesive film having a first surface and a secondsurface opposing the first surface, includes a first area and a secondarea disposed at positions different from each other in a thicknessdirection from the first surface toward the second surface, wherein amodulus of the first area is different from a modulus of the secondarea.

The adhesive film may form a single layer including the first area andthe second area without an interface between the first surface and thesecond surface.

A maximum value of a modulus of the adhesive film may be about 100 Kpaor higher and about 1000 Kpa or lower, and a minimum value of themodulus of the adhesive film may be about 100 Kpa or lower.

A deviation of a modulus of the adhesive film in the thickness directionmay be about 100 Kpa or greater.

A maximum value of a bending stiffness of the adhesive film may be about30 N·cm or higher and about 50 N·cm or lower, and a minimum value of thebending stiffness of the adhesive film may be about 15 N·cm or higherand about 30 N·cm or lower.

A modulus of the adhesive film may increase gradually along thethickness direction.

The first area may include a third area having a modulus that decreasesgradually along the thickness direction, and the second area may includea fourth area having a modulus that increases gradually along thethickness direction.

The adhesive film may further include a third area disposed between thefirst area and the second area, wherein each of the modulus of the firstarea and the modulus of the second area may be higher than a modulus ofthe third area.

The adhesive film may further include a third area disposed between thefirst area and the second area, wherein each of the modulus of the firstarea and the modulus of the second area may be lower than a modulus ofthe third area.

According to still yet another aspect of the invention, an adhesive filmfor a display device includes a first surface and a second surfaceopposing the first surface without an interface between the firstsurface and the second surface, wherein a modulus of the first surfaceis higher than a modulus of the second surface.

Accordingly to one aspect of the invention, a method of manufacturing anadhesive film for a display device, the method includes: forming, on afirst release film, a first composition including a resin and a firstinitiator for initiating a polymerization reaction of the resin;forming, on the first composition which has been applied, a secondcomposition including the resin and a second initiator for initiatingthe polymerization reaction of the resin; irradiating the firstcomposition and the second composition, which have been applied, withlight having a first range of wavelengths; and irradiating the firstcomposition and the second composition, which have been applied, withlight having a second range of wavelengths, wherein the first initiatorinitiates the polymerization reaction of the resin with the light havingthe first range of wavelengths without activating initiation of thepolymerization reaction with the light having the second range ofwavelengths, and wherein the second initiator initiates thepolymerization reaction of the resin with the light having the secondrange of wavelengths without activating the initiation of thepolymerization reaction with the light having the first range ofwavelengths.

The method may further include: forming, on the second composition, athird composition including the resin and a third initiator, wherein thethird initiator initiates the polymerization reaction of the resin withlight having a third range of wavelengths without activating theinitiation of the polymerization reaction with the light having thesecond range of wavelengths.

The third initiator may initiate the polymerization reaction of theresin with the light having the third range of wavelengths withoutactivating the initiation of the polymerization reaction with the lighthaving the first range of wavelengths.

An irradiation time of the light having the first range of wavelengthsmay be different from an irradiation time of the light having the secondrange of wavelengths.

Intensity of the light having the first range of wavelengths may bedifferent from intensity of the light having the second range ofwavelengths.

A concentration of the first initiator with respect to the firstcomposition is different from a concentration of the second initiatorwith respect to the second composition.

The forming of the second composition on the first composition mayinclude: applying the second composition on a second release film; andlaminating the first release film and the second release film on eachother in a state in which the first composition and the secondcomposition, which have been applied, face each other.

The forming of the first composition on the first release film mayinclude: applying the first initiator on the first release film; andapplying the resin on the first initiator which has been applied. Theapplying of the second composition on the second release film mayinclude: applying the second composition on the second release film; andapplying the resin on the second initiator which has been applied.

According to another aspect of the invention, a method of manufacturingan adhesive film for a display device includes: applying an initiator toa release film; applying a resin on the initiator which has beenapplied; and irradiating the initiator and the resin, which have beenapplied, with light.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the inventive concepts.

FIG. 1 is a perspective view of a display device constructed accordingto the principles of the invention.

FIG. 2 is a cross-sectional view illustrating a state in which thedisplay device of FIG. 1 is folded.

FIG. 3 is a cross-sectional view illustrating a state in which thedisplay device of FIG. 1 is rolled.

FIG. 4 is a plan view of an embodiment of some of pixels of a displaydevice.

FIG. 5 is a cross-sectional view taken along line I-I′ of FIG. 4.

FIG. 6 is a perspective view of an embodiment of a plurality of adhesivelayers.

FIG. 7 is a graph illustrating a modulus of an embodiment of a pluralityof adhesive layers.

FIG. 8 is a perspective view of an embodiment of an adhesive layer.

FIGS. 9 to 12 are graphs illustrating moduli of embodiments of anadhesive layer.

FIG. 13 is a graph illustrating a modulus of another embodiment of aplurality of adhesive layer.

FIGS. 14 to 16 are graphs illustrating moduli of other embodiments of anadhesive layer.

FIG. 17 is a perspective view of another embodiment of an adhesivelayer.

FIGS. 18 to 20 are graphs illustrating moduli of still other embodimentsof an adhesive layer.

FIGS. 21 to 28 are graphs each illustrating a concentration of aninitiator before curing an adhesive layer according to embodiments.

FIGS. 29A to 29G are cross-sectional views illustrating an embodiment ofa method of manufacturing an adhesive layer.

FIGS. 30A to 30C are cross-sectional views illustrating anotherembodiment of a method of manufacturing an adhesive layer.

FIGS. 31A to 31F are cross-sectional views illustrating still anotherembodiment of a method of manufacturing an adhesive layer.

FIGS. 32A to 32D are cross-sectional views illustrating yet anotherembodiment of a method of manufacturing an adhesive layer.

FIGS. 33A to 33E are cross-sectional views illustrating still yetanother embodiment of a method of manufacturing an adhesive layer.

FIGS. 34 and 35 are graphs each illustrating a concentration of aninitiator before curing an adhesive layer according to embodiments.

FIGS. 36A to 36E are cross-sectional views illustrating yet stillanother embodiment of a method of manufacturing an adhesive layer.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various embodiments may bepracticed without these specific details or with one or more equivalentarrangements. In other instances, well-known structures and devices areshown in block diagram form in order to avoid unnecessarily obscuringvarious embodiments. Further, various embodiments may be different, butdo not have to be exclusive. For example, specific shapes,configurations, and characteristics of an embodiment may be used orimplemented in another embodiment without departing from the inventiveconcepts.

Unless otherwise specified, the illustrated embodiments are to beunderstood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anembodiment may be implemented differently, a specific process order maybe performed differently from the described order. For example, twoconsecutively described processes may be performed substantially at thesame time or performed in an order opposite to the described order.Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z-axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various embodiments are described herein with reference to sectionaland/or exploded illustrations that are schematic illustrations ofidealized embodiments and/or intermediate structures. As such,variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

FIG. 1 is a perspective view of a display device constructed accordingto the principles of the invention. FIG. 2 is a cross-sectional viewillustrating a state in which the display device of FIG. 1 is folded.FIG. 3 is a cross-sectional view illustrating a state in which thedisplay device of FIG. 1 is rolled.

Referring to FIG. 1, a display device DD includes a display panel DP atwhich images are displayed, a cover member CM disposed on the side whereimages are displayed, and an adhesive layer PSA for attaching thedisplay panel DP and the cover member CM.

In an embodiment, the display device DD may include any one of a liquidcrystal display (LCD) panel, a light emitting diode (LED) display panel,an organic light emitting diode (OLED) display panel, or amicroelectromechanical system (MEMS) display panel, and an electronicpaper display panel.

The display device DD, i.e., the display panel DP and the cover memberCM, may be provided in a flat state as illustrated in FIG. 1, but it maybe provided in a different shape with at least part of the display panelDP and the cover member CM being transformed.

Referring to FIGS. 2 and 3 together with FIG. 1, at least part of thedisplay device DD may have flexibility, or the entirety of the displaydevice DD may have flexibility. Since the display device DD hasflexibility, the display device DD may be folded as illustrated in FIG.2 or rolled as illustrated in FIG. 3, in a flexible area.

Referring to FIG. 2, a folding line FL, along which the display deviceDD is folded, may pass through the center of the display device DD andmay be parallel to a third direction D3. However, the position of thefolding line FL is not limited thereto, and may be provided in adirection parallel to a second direction D2, or in a direction obliqueto the second direction D2 or the third direction D3. In addition, it isobviously not necessary that the folding line FL passes through thecenter of the display device DD.

In addition, the display device DD may be provided in an infoldingscheme in which an image display surface is folded inwardly along thefolding line FL not to be viewed, or in an outfolding scheme in whichthe image display surface is folded outwardly along the folding line FLto be viewed. In addition, when the display device DD is folded along aplurality of folding lines FL, part of the image display surface may befolded inwardly and another part of the image display surface may befolded outwardly.

A first direction D1 refers to a direction perpendicular to the seconddirection D2 and the third direction D3. The first direction D1corresponds to a thickness direction of the display device DD, thedisplay panel DP, the cover member CM, and the adhesive layer PSA. Inthe following description, the first direction D1 is defined as thedirection from the cover member CM toward the display panel DP. A lengthof the display device DD in the second direction D2 may be greater thana length of the display device DD in the third direction D3. The firstdirection D1, the second direction D2, and the third direction D3 may bereferred to as a thickness direction, a width direction, and a lengthdirection of the display device DD, the display panel DP, the adhesivelayer PSA, or the cover member CM, respectively.

Referring to FIG. 3, the display device DD may be rollable so that onesurface faces and/or contact another surface. A direction in which thedisplay device DD is rolled may be the second direction D2 or the thirddirection D3. However, embodiments are not limited thereto. For example,the display device DD may be rolled in a direction oblique to the seconddirection D2 or the third direction D3. In addition, in the displaydevice DD, the rolled area may be part of the display device DD, or theentire area of the display device DD may be rolled.

Although flexibility has been described with reference to the displaydevice DD for convenience of description, it may be applied to thedisplay panel DP, the cover member CM, the adhesive layer PSA, and/ortheir layers.

FIG. 4 is a plan view of an embodiment of some of pixels of a displaydevice. FIG. 5 is a cross-sectional view taken along line I-I′ of FIG.4.

Referring to FIGS. 4 and 5, an OLED display device DD includes asubstrate 100, a wiring unit 200, an OLED 300, and a thin filmencapsulation layer 350. The OLED display device DD may further includea buffer layer 120 and a pixel defining layer 190.

The substrate 110 may include an insulating material selected from thegroup consisting of glass, quartz, ceramic, and plastic. However,embodiments are not limited thereto, and the substrate 100 may include ametal material, such as stainless steel.

The buffer layer 120 is disposed on the substrate 110. The buffer layer120 may include one or more layers selected from various inorganiclayers and organic layers. The buffer layer 120 serves to preventunnecessary substances, e.g., impurities or moisture, from penetratinginto the wiring unit 200 or the OLED 300, and to planarize a surfacetherebelow. However, the buffer layer 120 is not necessarily requiredand may be omitted depending on the type of the substrate 100 and theprocess conditions.

The wiring unit 200 is disposed on the buffer layer 120. The wiring unit200 includes a plurality of thin film transistors (TFTs) 10 and 20, anddrives the OLED 300. That is, the OLED 300 emits light according to adriving signal received from the wiring unit 200 to display images.

FIGS. 4 and 5 illustrate an active matrix-type organic light emittingdiode (AMOLED) display device having a 2Tr-1Cap structure which includestwo TFTs 10 and 20, and one capacitor 80 in each pixel PX. However,embodiments are not limited thereto, and the OLED display device DD mayinclude three or more transistors and two or more capacitors in eachpixel, and may have various structures including additional wirings.Herein, a pixel refers to a minimum unit for displaying an image, andthe OLED display device DD displays images through a plurality ofpixels.

Each pixel includes a switching TFT 10, a driving TFT 20, the capacitor80, and the OLED 300. A configuration of the switching TFT 10, thedriving TFT 20, and the capacitor 80 is collectively referred to as thewiring unit 200. In addition, a gate line 151 extending along adirection, and a data line 171 and a common power line 172 insulatedfrom and intersecting the gate line 151 are disposed at the wiring unit200. Each pixel may be defined by the gate line 151, the data line 171,and the common power line 172, which serve as a boundary, butembodiments are not limited thereto. The pixels may be defined by thepixel defining layer 190.

The OLED 300 includes a first electrode 310, an organic light emittinglayer 320 on the first electrode 310, and a second electrode 330 on theorganic light emitting layer 320. Holes and electrons are applied fromthe first electrode 310 and the second electrode 330, respectively, intothe organic light emitting layer 320 and then combined with each othertherein to form an exciton. When the exciton falls from an excited stateto a ground state, light is emitted.

The capacitor 80 includes a pair of capacitor plates 158 and 178, havingan insulating interlayer 160 interposed therebetween. In such anembodiment, the insulating interlayer 160 may be a dielectric element. Acapacitance of the capacitor 80 is determined by electric chargesaccumulated in the capacitor 80 and a voltage across the pair ofcapacitor plates 158 and 178.

The switching TFT 10 includes a switching semiconductor layer 131, aswitching gate electrode 152, a switching source electrode 173, and aswitching drain electrode 174. The driving TFT 20 includes a drivingsemiconductor layer 132, a driving gate electrode 155, a driving sourceelectrode 176, and a driving drain electrode 177. A gate insulatinglayer 130 is provided to insulate the semiconductor layers 131 and 132and the gate electrodes 152 and 155.

The switching TFT 10 may function as a switching element which selects apixel to perform light emission. The switching gate electrode 152 isconnected to the gate line 151, and the switching source electrode 173is connected to the data line 171. The switching drain electrode 174 isspaced apart from the switching source electrode 173 and connected toone of the capacitor plates, e.g., the capacitor plate 158.

The driving TFT 20 applies a driving power, which allows the organiclight emitting layer 320 of the OLED 300 in a selected pixel to emitlight, to the first electrode 310 which is a pixel electrode. Thedriving gate electrode 155 is connected to the capacitor plate 158 thatis connected to the switching drain electrode 174. Each of the drivingsource electrode 176 and the other of the capacitor plates, e.g., thecapacitor plate 178, is connected to the common power line 172. Thedriving drain electrode 177 is connected to the first electrode 310 ofthe OLED 300 through a contact hole.

With the above-described structure, the switching TFT 10 is operatedbased on a gate voltage applied to the gate line 151 and serves totransmit a data voltage applied to the data line 171 to the driving TFT20. A voltage equivalent to a difference between a common voltageapplied to the driving TFT 20 from the common power line 172 and thedata voltage transmitted by (or from) the switching TFT 10 is stored inthe capacitor 80, and a current corresponding to the voltage stored inthe capacitor 80 flows to the OLED 300 through the driving TFT 20 suchthat the OLED 300 may emit light.

The OLED 300 emits light according to the driving signal received fromthe wiring unit 200. In addition, the OLED 300 may include the firstelectrode 310 serving as an anode for injecting holes, the secondelectrode 330 serving as a cathode for injecting electrons, and theorganic light emitting layer 320 disposed between the first electrode310 and the second electrode 330. That is, the first electrode 310, theorganic light emitting layer 320, and the second electrode 330 aresequentially stacked to form the OLED 300. However, embodiments are notlimited thereto. For example, the first electrode 310 may serve as acathode and the second electrode 330 may serve as an anode.

In an embodiment, the first electrode 310 may include a reflective film,and the second electrode 330 may include a transflective film.Accordingly, light generated in the organic light emitting layer 320 maypass through the second electrode 330 to be emitted outwards. That is,the OLED display device DD may have a top-emission type structure.

In an embodiment, the transflective film and the reflective film mayinclude one or more of metals, e.g., magnesium (Mg), silver (Ag), gold(Au), calcium (Ca), lithium (Li), chromium (Cr), and aluminum (Al), oran alloy thereof. In such an embodiment, whether the film is atransflective type or a reflective type depends on the thickness of thefilm. Typically, the transflective film has a thickness of about 200 nmor less. As the thickness of the transflective film decreases, lighttransmittance increases, and as the thickness of the transflective filmincreases, light transmittance decreases.

In addition, the first electrode 310 may include a transparentconductive film. That is, the first electrode 310 may have a multilayerstructure including a reflective film and a transparent conductive film.The transparent conductive film of the first electrode 310 is disposedbetween the reflective film and the organic light emitting layer 320. Inaddition, the first electrode 310 may have a triple-layer structure inwhich a transparent conductive film, a reflective film, and atransparent conductive film are sequentially stacked. The firstelectrode 310 may only include a transparent conductive film. In such acase, the first electrode 310 becomes a transparent electrode.

The transparent conductive film may include transparent conductive oxide(TCO) such as indium tin oxide (ITO), indium zinc oxide (IZO), zincoxide (ZnO), or indium oxide (In₂O₃). The transparent conductive filmhas a relatively high work function. Accordingly, when the firstelectrode 310 includes a transparent conductive film, hole injectionthrough the first electrode 310 is facilitated.

The second electrode 330 may include a transparent conductive film. Whenthe second electrode 330 includes a transparent conductive film, thesecond electrode 330 may be an anode for injecting holes. In such anembodiment, the first electrode 310 may only include a reflective filmto serve as a cathode.

At least one of a hole injection layer HIL and a hole transporting layerHTL may further be disposed between the first electrode 310, whichserves as an anode, and the organic light emitting layer 320, and atleast one of an electron transporting layer ETL and an electroninjection layer EIL may further be disposed between the organic lightemitting layer 320 and the second electrode 330, which serves as acathode.

In an embodiment, an additional layer may be further disposed betweenthe organic light emitting layer 320 and the first electrode 310 andbetween the organic light emitting layer 320 and the second electrode330.

The pixel defining layer 190 has an opening 195. The opening 195 of thepixel defining layer 190 exposes part of the first electrode 310. Thefirst electrode 310, the organic light emitting layer 320, and thesecond electrode 330 are sequentially stacked in the opening 195 of thepixel defining layer 190. In such an embodiment, the second electrode213 may also be disposed on the pixel defining layer 190, as well as onthe organic light emitting layer 320. In addition, the HIL, the HTL, theETL, and the EIL may also be disposed between the pixel defining layer190 and the second electrode 330. The OLED 300 emits light from theorganic light emitting layer 320 in the opening 195 of the pixeldefining layer 190. As such, the opening 195 of the pixel defining layer190 defines a light emission area.

The thin film encapsulation layer 350 is disposed on the secondelectrode 330. The thin film encapsulation layer 350 seals the firstelectrode 310, the OLED 320, and the second electrode 330, and protectsthem from the external environment.

The thin film encapsulation layer 350 may have a structure in which atleast one organic layer 370 and at least one inorganic layer 360 and 380are alternately disposed. However, embodiments are not limited thereto,and the thin film encapsulation layer 350 may include a single layer ofan organic layer or an inorganic layer.

The display panel DP may include, for example, a touch sensing layer, apolarization layer, and a color filter layer disposed on the thin filmencapsulation layer 350.

The cover member CM is disposed on a front surface of the display panelDP on which images are displayed. The adhesive layer PSA is interposedbetween the cover member CM and the front surface of the display panelDP. The cover member CM may transmit light generated by the displaypanel DP.

The cover member CM may include, for example, a window including aflexible material such as tempered glass, tempered plastic, or a polymermaterial. The window may be a flexible glass in the form of a thin film.The glass window in the form of a thin film may have a thickness ofabout 100 μm or less, and more preferably about 75 μm or less.

The cover member CM may further include a protective film attached tothe front surface or a rear surface of the window. In addition, thecover member CM may include a touch sensing layer, a polarization layer,a color filter layer, or the like disposed at the front surface or therear surface of the window. In addition, the cover member CM may includea light blocking layer and a hard coating layer formed at the frontsurface or the rear surface of the window.

The adhesive layer PSA is disposed between the cover member CM and thedisplay panel DP to attach them to each other. The adhesive layer PSAmay directly contact an upper surface of the display panel DP and alower surface of the cover member CM. The adhesive layer PSA may includea pressure sensitive adhesive or an optical cleared adhesive.

FIG. 6 is a perspective view of an embodiment of a plurality of adhesivelayers. FIG. 7 is a graph illustrating a modulus of an embodiment of aplurality of adhesive layers.

Referring to FIG. 6, at least two adhesive layers PAS1 and PSA2 may beprovided between the cover member CM and the display panel DP of FIG. 1.The first adhesive layer PAS1 has a front surface S11 facing the covermember CM and a rear surface S12 facing the display panel DP. The secondadhesive layer PAS2 has a front surface S21 facing the cover member CMand a rear surface S22 facing the display panel DP. The front surfaceS11 of the first adhesive layer PSA1 may directly contact the covermember CM, or the window of the cover member CM. The rear surface S22 ofthe second adhesive layer PAS2 may directly contact the display panelDP, or the thin film encapsulation layer 350 of the display panel DP.The rear surface S12 of the first adhesive layer PSA1 and the frontsurface S21 of the second adhesive layer PSA2 contact each other.

Referring to FIG. 7, the first adhesive layer PSA1 has a modulus higherthan a modulus of the second adhesive layer PSA2. Each of the firstadhesive layer PSA1 and the second adhesive layer PSA2 may have asubstantially constant modulus in the first direction D1 which is thethickness direction. The modulus of the first adhesive layer PSA1, orthe front surface S11 of the first adhesive layer PSA1 may be about 100Kpa or higher and about 1000 Kpa or lower, and the modulus of the secondadhesive layer PSA2, or the rear surface S22 of the second adhesivelayer PSA2 may be about 100 Kpa or lower. A difference between themodulus of the first adhesive layer PSA1, or the front surface S11 ofthe first adhesive layer PSA1 and the modulus of the second adhesivelayer PSA2, or the rear surface S22 of the second adhesive layer PSA2may be about 100 Kpa or greater.

The first adhesive layer PSA1 has a bending stiffness higher than abending stiffness of the second adhesive layer PSA2. Each of the firstadhesive layer PSA1 and the second adhesive layer PSA2 may have asubstantially constant bending stiffness in the first direction D1 whichis the thickness direction. The bending stiffness of the first adhesivelayer PSA1, or the front surface S11 of the first adhesive layer PSA1may be about 30 N·cm or higher and about 50 N·cm or lower, and thebending stiffness of the second adhesive layer PSA2, or the rear surfaceS22 of the second adhesive layer PSA2 may be about 15 N·cm or higher andabout 30 N·cm or lower. A difference between the bending stiffness ofthe first adhesive layer PSA1, or the front surface S11 of the firstadhesive layer PSA1 and the bending stiffness of the second adhesivelayer PSA2, or the rear surface S22 of the second adhesive layer PSA2may be about 15 N·cm or greater.

The first adhesive layer PSA1 having a relatively high modulus and arelatively high bending stiffness may substantially prevent the covermember CM, or the window of the cover member CM from being damaged whenthe display device is folded, and the adhesive layer PSA2 having arelatively low modulus and a relatively low bending stiffness maysubstantially prevent bright spots from being generated by an impactapplied to the display panel DP.

FIG. 8 is a perspective view of an embodiment of an adhesive layer.FIGS. 9 to 12 are graphs illustrating moduli of embodiments of anadhesive layer. In FIGS. 9 to 12, a vertical axis denotes a modulus orbending stiffness, and the horizontal axis denotes a position in thefirst direction D1.

Referring to FIG. 8, an adhesive layer PAS3 may be provided between thecover member CM and the display panel DP of FIG. 1. The adhesive layerPAS3 has a front surface S1 facing the cover member CM and a rearsurface S2 facing the display panel DP. The front surface S1 of theadhesive layer PSA3 may directly contact the cover member CM, or thewindow of the cover member CM. The rear surface S2 of the adhesive layerPAS3 may directly contact the display panel DP, or the thin filmencapsulation layer 350 of the display panel DP. Since the adhesivelayer PAS3 forms a single layer, the adhesive layer PAS3 does notinclude an interface between the front surface S1 and the rear surfaceS2 of the adhesive layer PSA3.

The adhesive layer PAS3 may include first and second areas defined to bedisposed at different positions from each other in the first directionD1, and the first and second areas may have different moduli from eachother

Referring to FIG. 9, the front surface S1 of the adhesive layer PSA3 hasa modulus or bending stiffness higher than that of the rear surface S2.The adhesive layer PSA3 may have a modulus or bending stiffness thatdecreases gradually in the first direction D1, which is a direction fromthe front surface S1 toward the rear surface S2, at a first region R1throughout the adhesive layer PSA3. A modulus variation slope may be thegreatest at a first point P1 between the front surface S1 and the rearsurface S2, for example, at a point separated by substantially the samedistance from the front surface S1 and the rear surface S2, and themodulus variation slope may decrease gradually, as further away from thefirst point P1.

The modulus of the adhesive layer PSA3 at the front surface S1 may beabout 100 Kpa or higher and about 1000 Kpa or lower, and the modulus ofthe adhesive layer PSA3 at the rear surface S2 may be about 100 Kpa orlower. A difference between the modulus of the adhesive layer PSA3 atthe front surface S1 and the modulus of the adhesive layer PSA3 at therear surface S2 may be about 100 Kpa or greater.

The adhesive layer PSA3 has a higher bending stiffness at the frontsurface S1 than that at the rear surface S2. The adhesive layer PSA3 mayhave a bending stiffness that decreases gradually in the first directionD1. The bending stiffness of the adhesive layer PSA3 at the frontsurface S1 may be about 30 N·cm or higher and about 50 N·cm or lower,and the bending stiffness of the adhesive layer PSA3 at the rear surfaceS2 may be about 15 N·cm or higher and about 30 N·cm or lower. Adifference between the bending stiffness of the adhesive layer PSA3 atthe front surface S1 and the bending stiffness of the adhesive layerPSA3 at the rear surface S2 may be about 15 N·cm or greater.

The front surface S1 of the adhesive layer PSA3 having a relatively highmodulus and a relatively high bending stiffness may prevent or at leastreduce the cover member CM, or the window of the cover member CM frombeing damaged when the display device is folded, and the rear surface S2of the adhesive layer PSA3 having a relatively low modulus and arelatively low bending stiffness may prevent or at least reduce brightspots from being generated by an impact applied to the display panel DP.Also, since the adhesive layer PSA3 forms a single layer, themanufacturing process of the display device may be reduced (simplified).In addition, since the single adhesive layer PSA3 may prevent or atleast reduce reflection or refraction of light that may occur at aninterface between a plurality of adhesive layers such as adhesive layersPSA1 and PSA2 of FIG. 6, the image quality of the display device may beimproved. In addition, given that a plurality of adhesive layers maypeel off from each other, the single adhesive layer PSA3 may be robustto stress.

Referring to FIG. 10, the front surface S1 of the adhesive layer PSA3has a modulus lower than that of the rear surface S2. The adhesive layerPSA3 may have a modulus that increases gradually in the first directionD1. The modulus of the adhesive layer PSA3 at the front surface S1 maybe about 100 Kpa or lower, and the modulus of the adhesive layer PSA3 atthe rear surface S2 may be about 100 Kpa or higher and about 1000 Kpa orlower. A difference between the modulus of the adhesive layer PSA3 atthe front surface S1 and the modulus of the adhesive layer PSA3 at therear surface S2 may be about 100 Kpa or greater.

The adhesive layer PSA3 has a lower bending stiffness at the frontsurface S1 than that at the rear surface S2. The adhesive layer PSA3 mayhave a bending stiffness that increases gradually in the first directionD1. The bending stiffness of the adhesive layer PSA3 at the rear surfaceS2 may be about 30 N·cm or higher and about 50 N·cm or lower, and thebending stiffness of the adhesive layer PSA3 at the front surface S1 maybe about 15 N·cm or higher and about 30 N·cm or lower. A differencebetween the bending stiffness of the adhesive layer PSA3 at the frontsurface S1 and the bending stiffness of the adhesive layer PSA3 at therear surface S2 may be about 15 N·cm or greater.

Referring to FIG. 11, the front surface S1 of the adhesive layer PSA3has a modulus or bending stiffness higher than that of the rear surfaceS2. The adhesive layer PSA3 may have a substantially constant modulus orbending stiffness at the second region R2 from the front surface S1 tothe second point P2. The adhesive layer PSA3 may have a modulus orbending stiffness that decreases gradually in the first direction D1 atthe first region R1 from the second point P2 to a third point P3. Theadhesive layer PSA3 may have a substantially constant modulus or bendingstiffness at a third region R3 from the third point P3 to the rearsurface S2. The adhesive layer PSA3 has a continuous modulus or bendingstiffness throughout the entire regions R1, R2, and R3 of the adhesivelayer PSA3.

The modulus of the adhesive layer PSA3 at the second region R2 may beabout 100 Kpa or higher and about 1000 Kpa or lower, and the modulus ofthe adhesive layer PSA3 at the third region R3 may be about 100 Kpa orlower. A difference between the modulus of the adhesive layer PSA3 atthe second region R2 and the modulus of the adhesive layer PSA3 at thethird region R3 may be about 100 Kpa or greater.

The bending stiffness of the adhesive layer PSA3 at the second region R2may be about 30 N·cm or higher and about 50 N·cm or lower, and thebending stiffness of the adhesive layer PSA3 at the third region R3 maybe about 15 N·cm or higher and about 30 N·cm or lower. A differencebetween the bending stiffness of the adhesive layer PSA3 at the secondregion R2 and the bending stiffness of the adhesive layer PSA3 at thethird region R3 may be about 15 N·cm or greater.

Referring to FIG. 12, the front surface S1 of the adhesive layer PSA3has a modulus or bending stiffness lower than that of the rear surfaceS2. The adhesive layer PSA3 may have a substantially constant modulus orbending stiffness at the second region R2 from the front surface S1 tothe second point P2. The adhesive layer PSA3 may have a modulus orbending stiffness that increases gradually in the first direction D1 atthe first region R1 from the second point P2 to the third point P3. Theadhesive layer PSA3 may have a substantially constant modulus or bendingstiffness at the third region R3 from the third point P3 to the rearsurface S2. The adhesive layer PSA3 has a continuous a modulus orbending stiffness throughout the entire regions R1, R2, and R3 of theadhesive layer PSA3.

The modulus of the adhesive layer PSA3 at the second region R2 may beabout 100 Kpa or lower, and the modulus of the adhesive layer PSA3 atthe third region R3 may be about 100 Kpa or higher and about 1000 Kpa orlower. A difference between the modulus of the adhesive layer PSA3 atthe second region R2 and the modulus of the adhesive layer PSA3 at thethird region R3 may be about 100 Kpa or greater.

The bending stiffness of the adhesive layer PSA3 at the second region R2may be about 15 N·cm or higher and about 30 N·cm or lower, and thebending stiffness of the adhesive layer PSA3 at the third region R3 maybe about 30 N·cm or higher and about 50 N·cm or lower. A differencebetween the bending stiffness of the adhesive layer PSA3 at the secondregion R2 and the bending stiffness of the adhesive layer PSA3 at thethird region R3 may be about 15 N·cm or greater.

FIG. 13 is a graph illustrating a modulus of another embodiment of aplurality of adhesive layer.

Referring to FIG. 13, a plurality of adhesive layers PAS1, PSA2, andPSA3 may be provided between the cover member CM and the display panelDP of FIG. 1. The third adhesive layer PSA3 may be disposed between thefirst adhesive layer PSA1 and the second adhesive layer PSA2. The thirdadhesive layer PSA3 may be the adhesive layer PSA3 illustrated withreference to FIGS. 8 to 12. The first adhesive layer PSA1 and the secondadhesive layer PSA2 form interfaces S1 and S2 with the third adhesivelayer PSA3. A front surface S4 of the first adhesive layer PSA1 maydirectly contact the cover member CM, or the window of the cover memberCM. A rear surface S5 of the second adhesive layer PAS2 may directlycontact the display panel DP, or the thin film encapsulation layer 350of the display panel DP.

At the interface S1 between the first adhesive layer PSA1 and the thirdadhesive layer PSA3, and at the interface S2 between the second adhesivelayer PSA2 and the third adhesive layer PSA3, a modulus or bendingstiffness of the adhesive layer PSA1, PSA2, and PSA3 may not becontinuous. The modulus or bending stiffness of the first adhesive layerPSA1 may be higher than the modulus or bending stiffness of the thirdadhesive layer PSA3. The modulus or bending stiffness of the secondadhesive layer PSA2 may be lower than the modulus or bending stiffnessof the third adhesive layer PSA3. The first adhesive layer PSA1 and thesecond adhesive layer PSA2 may each have a substantially constantmodulus in the first direction D1 which is the thickness direction.

FIGS. 14 to 16 are graphs illustrating moduli of other embodiments of anadhesive layer.

Referring to FIG. 14, the front surface S1 and the rear surface S2 ofthe adhesive layer PSA3 have moduli or bending stiffnesses higher thanthe modulus or bending stiffness of a fourth point P4 therebetween. Theadhesive layer PSA3 may have a modulus or bending stiffness thatdecreases gradually in the first direction D1 at a (1-1)-th region R1-1from the front surface S1 to the fourth point P4. The adhesive layerPSA3 may have a modulus or bending stiffness that increases gradually inthe first direction D1 at a (1-2)-th region R1-2 from the fourth pointP4 to the rear surface S2. A modulus variation slope may be the greatestat a fifth point P5 between the front surface S1 and the fourth point P4and at a sixth point P6 between the rear surface S2 and the fourth pointP4, and may decrease gradually, as further away from the fifth point P5and the sixth point P6.

The modulus of the adhesive layer PSA3 at the front surface S1 and therear surface S2 may be about 100 Kpa or higher and about 1000 Kpa orlower, and the modulus of the adhesive layer PSA3 at the fourth point P4may be about 100 Kpa or lower. A difference between the modulus of theadhesive layer PSA3 at the front surface S1 and the rear surface S2 andthe modulus of the adhesive layer PSA3 at the fourth point P4 may beabout 100 Kpa or greater.

The bending stiffness of the adhesive layer PSA3 at the front surface S1and the rear surface S2 may be about 30 N·cm or higher and about 50 N·cmor lower, and the bending stiffness of the adhesive layer PSA3 at thefourth point P4 may be about 15 N·cm or higher and about 30 N·cm orlower. A difference between the bending stiffness of the adhesive layerPSA3 at the front surface S1 and the rear surface S2 and the bendingstiffness of the adhesive layer PSA3 at the fourth point P4 may be about15 N·cm or greater.

Referring to FIG. 15, the front surface S1 and the rear surface S2 ofthe adhesive layer PSA3 have a modulus or bending stiffness higher thanthat of the fourth point P4 therebetween. The adhesive layer PSA3 mayhave a substantially constant modulus or bending stiffness, within apredetermined distance from the front surface S1, and within apredetermined distance from the fourth point P4, and within apredetermined distance from the rear surface S2.

Referring to FIG. 16, the front surface S1 and the rear surface S2 ofthe adhesive layer PSA3 have a modulus or bending stiffness lower thanthat of the fourth point P4 therebetween. The adhesive layer PSA3 mayhave a modulus or bending stiffness that decreases gradually in thefirst direction D1 at the (1-1)-th region R1-1 from the fourth point P4to the rear surface S2. The adhesive layer PSA3 may have a modulus orbending stiffness that increases gradually in the first direction D1 atthe (1-2)-th region R1-2 from the front surface S1 to the fourth pointP4. A modulus variation slope is the greatest at the fifth point P5between the front surface S1 and the fourth point P4 and at the sixthpoint P6 between the rear surface S2 and the fourth point P4, and maydecrease gradually, as further away from the fifth point P5 and thesixth point P6.

The modulus of the adhesive layer PSA3 at the front surface S1 and therear surface S2 may be about 100 Kpa or lower, and the modulus of theadhesive layer PSA3 at the fourth point P4 may be about 100 Kpa orhigher and about 1000 Kpa or lower. A difference between the modulus ofthe adhesive layer PSA3 at the front surface S1 and the rear surface S2and the modulus of the adhesive layer PSA3 at the fourth point P4 may beabout 100 Kpa or greater.

The bending stiffness of the adhesive layer PSA3 at the front surface S1and the rear surface S2 may be about 15 N·cm or higher and about 30 N·cmor lower, and the bending stiffness of the adhesive layer PSA3 at thefourth point P4 may be about 30 N·cm or higher and about 50 N·cm orlower. A difference between the bending stiffness of the adhesive layerPSA3 at the front surface S1 and the rear surface S2 and the bendingstiffness of the adhesive layer PSA3 at the fourth point P4 may be about15 N·cm or greater.

The adhesive layer PSA3 may have a substantially constant modulus orbending stiffness, within a predetermined distance from the frontsurface S1, within a predetermined distance from the fourth point P4,and within a predetermined distance from the rear surface S2.

FIG. 17 is a perspective view of another embodiment of an adhesivelayer. FIGS. 18 to 20 are graphs illustrating moduli of still otherembodiments of an adhesive layer. In FIGS. 18 to 20, a vertical axisdenotes a modulus or bending stiffness, and a horizontal axis denotes aposition in the second direction D2.

Referring to FIGS. 1 and 17, the folding line FL, along which thedisplay device DD is folded, may pass through the center of the displaydevice DD and may be parallel to the third direction D3. Accordingly,the display device DD, the display panel DP, the cover member CM, andthe adhesive layer PSA3 have a folding area FA adjacent to the foldingline FL and the non-folding area NFA on opposite sides of the foldingarea FA.

The adhesive layer PAS3 may be disposed between the cover member CM andthe display panel DP. The adhesive layer PAS3 has a front surface S1facing the cover member CM and a rear surface S2 facing the displaypanel DP. The front surface S1 of the adhesive layer PSA3 may directlycontact the cover member CM, or the window of the cover member CM. Therear surface S2 of the adhesive layer PAS3 may directly contact thedisplay panel DP, or the thin film encapsulation layer 350 of thedisplay panel DP. The adhesive layer PAS3 forms a single layer withoutan interface between the front surface S1 and the rear surface S2. Theadhesive layer PSA3 has side surfaces S3 and 34 extending between thefront surface S1 and the rear surface S2. A first side surface S3 and asecond side surface S4 may extend in the third direction D3 crossing thesecond direction D2. The first side surface S3 and the second sidesurface S4 may be shaped to be parallel to the folding line FL. Aninterface may not be present between the first side surface S3 and thesecond side surface S4 of the adhesive layer PSA3.

Referring to FIG. 18, the folding area FA of the adhesive layer PSA3 hasa modulus or bending stiffness lower than that of the non-folding areaNFA. The adhesive layer PSA3 may have a modulus or bending stiffnessthat decreases gradually from the first side surface S3 toward a seventhpoint P7, which corresponds to the folding line FL. The adhesive layerPSA3 may have a modulus or bending stiffness that increases graduallyfrom the seventh point P7 to the second side surface S4. The modulusvariation slope may be the greatest at an eighth point P8 between thefirst side face S3 and the seventh point P7 and at a ninth point P9between the second side face S4 and the seventh point P7, and maydecrease gradually, as further away from the eighth and ninth points P8and P9. The eighth and ninth points P8 and P9 may correspond to aboundary between the folding area FA and the non-folding area NFA.

The modulus of the adhesive layer PSA3 at the non-folding area NFA maybe about 100 Kpa or higher and about 1000 Kpa or lower, and the modulusof the adhesive layer PSA3 at the folding area FA may be about 100 Kpaor lower. A difference between the modulus of the adhesive layer PSA3 atthe non-folding area NFA and the modulus of the adhesive layer PSA3 atthe folding area FA may be about 100 Kpa or greater.

The modulus of the adhesive layer PSA3 at the first and second sidesurfaces S3 and S4 may be about 100 Kpa or higher and about 1000 Kpa orlower, and the modulus of the adhesive layer PSA3 at the seventh pointP7 may be about 100 Kpa or lower. A difference between the modulus ofthe adhesive layer PSA3 at the first and second side surfaces S3 and S4and the modulus of the adhesive layer PSA3 at the seventh point P7 maybe about 100 Kpa or greater.

The bending stiffness of the adhesive layer PSA3 at the non-folding areaNFA may be about 30 N·cm or higher and about 50 N·cm or lower, and thebending stiffness of the adhesive layer PSA3 at the folding area FA maybe about 15 N·cm or higher and about 30 N·cm or lower. A differencebetween the bending stiffness of the adhesive layer PSA3 at thenon-folding area NFA and the bending stiffness of the adhesive layerPSA3 at the folding area FA may be about 15 N·cm or greater.

The bending stiffness of the adhesive layer PSA3 at the first and secondside surfaces S3 and S4 may be about 30 N·cm or higher and about 50 N·cmor lower, and the bending stiffness of the adhesive layer PSA3 at theseventh point P7 may be about 15 N·cm or higher and about 30 N·cm orlower. A difference between the bending stiffness of the adhesive layerPSA3 at the first and second side surfaces S3 and S4 and the bendingstiffness of the adhesive layer PSA3 at the seventh point P7 may beabout 15 N·cm or greater.

Referring to FIG. 19, the adhesive layer PSA3 may have a substantiallyconstant modulus or bending stiffness, within a predetermined distancefrom the first side surface S3, within a predetermined distance from theseventh point P7, and within a predetermined distance from the secondside surface S4. More specifically, the adhesive layer PSA3 may have asubstantially constant modulus or bending stiffness from the first sidesurface S3 to a tenth point P10. From the tenth point P10 to a twelfthpoint P12, the adhesive layer PSA3 may have a modulus or bendingstiffness that decreases gradually. From the twelfth point P12 to athirteenth point P13, the adhesive layer PSA3 may have a substantiallyconstant modulus or bending stiffness. From the thirteenth point P13 toan eleventh point P11, the adhesive layer PSA3 may have a modulus orbending stiffness that increases gradually. From the eleventh point P11to the second side surface S4, the adhesive layer PSA3 may have asubstantially constant modulus or bending stiffness.

The adhesive layer PSA3 having a relatively high modulus and arelatively high bending stiffness at the non-folding area NFA mayimprove impact resistance of the display device DD. The adhesive layerPSA3 having a relatively low modulus and a relatively low bendingstiffness at the folding area FA may relieve stress generated due to thefolding of the display device DD. Also, the single adhesive layer PSA3may enable the manufacturing process of the display device to bereduced. In addition, since the single adhesive layer PSA3 may preventor at least reduce reflection or refraction of light that may occur atan interface between a plurality of adhesive layers, the image qualityof the display device may be improved.

Referring to FIG. 20, the folding area FA of the adhesive layer PSA3 hasa modulus or bending stiffness higher than that of the non-folding areaNFA. The adhesive layer PSA3 may have a modulus or bending stiffnessthat increases gradually from the first side surface S3 to the seventhpoint P7, which corresponds to the folding line FL. The adhesive layerPSA3 may have a modulus or bending stiffness that decreases graduallyfrom the seventh point P7 to the second side surface S4.

The modulus of the adhesive layer PSA3 at the folding area FA may beabout 100 Kpa or higher and about 1000 Kpa or lower, and the modulus ofthe adhesive layer PSA3 at the non-folding area NFA may be about 100 Kpaor lower. A difference between the modulus of the adhesive layer PSA3 atthe folding area FA and the modulus of the adhesive layer PSA3 at thenon-folding area NFA may be about 100 Kpa or greater.

The modulus of the adhesive layer PSA3 at the seventh point P7 may beabout 100 Kpa or higher and about 1000 Kpa or lower, and the modulus ofthe adhesive layer PSA3 at the first and second side surfaces S3 and S4may be about 100 Kpa or lower. A difference between the modulus of theadhesive layer PSA3 at the first and second side surfaces S3 and S4 andthe modulus of the adhesive layer PSA3 at the seventh point P7 may beabout 100 Kpa or greater.

The bending stiffness of the adhesive layer PSA3 at the folding area FAmay be about 30 N·cm or higher and about 50 N·cm or lower, and thebending stiffness of the adhesive layer PSA3 at the non-folding area NFAmay be about 15 N·cm or higher and about 30 N·cm or lower. A differencebetween the bending stiffness of the adhesive layer PSA3 at thenon-folding area NFA and the bending stiffness of the adhesive layerPSA3 at the folding area FA may be about 15 N·cm or greater.

The bending stiffness of the adhesive layer PSA3 at the seventh point P7may be about 30 N·cm or higher and about 50 N·cm or lower, and thebending stiffness of the adhesive layer PSA3 at the first and secondside surfaces S3 and S4 may be about 15 N·cm or higher and about 30 N·cmor lower. A difference between the bending stiffness of the adhesivelayer PSA3 at the seventh point P7 and the bending stiffness of theadhesive layer PSA3 at the first and second side surfaces S3 and S4 maybe about 15 N·cm or greater.

Referring to FIG. 20, the adhesive layer PSA3 may have a substantiallyconstant modulus or bending stiffness, within a predetermined distancefrom the first side surface S3, within a predetermined distance from theseventh point P7, and within a predetermined distance from the secondside surface S4. More specifically, the adhesive layer PSA3 may have asubstantially constant modulus or bending stiffness from the first sidesurface S3 to the tenth point P10, from the twelfth point P12 to athirteenth point P13, and from the eleventh point P11 to the second sidesurface S4.

The third adhesive layer PSA3 having a relatively low modulus and arelatively low bending stiffness at the non-folding area NFA maysubstantially prevent bright spots from being generated by an impactapplied to the display panel DP. The third adhesive layer PSA3 having arelatively high modulus and a relatively high bending stiffness at thefolding area FA may substantially prevent or at least reduce bucklingdue to shearing forces of the adhesive layer PSA3, that may be generatedwhen the display device DD is folded, overlapping at some areas of thedisplay device DD such as the non-folding area NFA. Thus, the displaydevice DD may not be deformed. Also, the single adhesive layer PSA3 mayenable the manufacturing process of the display device to be simplified.In addition, since the single adhesive layer PSA3 may prevent or atleast reduce reflection or refraction of light that may occur at aninterface between a plurality of adhesive layers, the image quality ofthe display device may be improved.

FIGS. 21 to 28 are graphs each illustrating a concentration of aninitiator included in a composition before curing an adhesive layeraccording to embodiments. In FIGS. 21 to 28, a vertical axis denotes aconcentration of an initiator, and a horizontal axis denotes a positionin the first direction D1.

In an embodiment, the adhesive layer PSA3 may be formed by curing aphotocurable composition including a photocurable resin. Thephotocurable resin, more specifically, an ultraviolet (UV)—curableresin, includes a polymer material system or a composition system thatcauses physical and chemical changes by a light energy. Photocuring mayinclude photopolymerization in which monomers or photosensitive polymers(i.e., prepolymers) become polymers, or optical crosslinking in whichpolymers are converted into three-dimensional crosslinked polymers by acrosslinking reaction.

The UV-curable composition may include a prepolymer, a polyfunctionalmonomer (which is a diluent), and a photoinitiator component, and maygenerally include 50 to 60% of a polymer, 30 to 40% of a multifunctionalmonomer, and 1 to 10% of a photoinitiator.

The polyfunctional monomer serves as a diluent for the UV-curablecomposition to reduce the viscosity and becomes part of a curedstructure after curing. The polyfunctional monomer may include amonofunctional, bifunctional or polyfunctional acrylic system.

The prepolymer is a main component constituting the skeleton of theUV-curable composition, and determines the physical properties(hardness, adhesion, electrical properties, flexibility, chemicalresistance, etc.) of the adhesive layer PSA3. The prepolymer may includeat least one selected from the group consisting of unsaturated polyesterresins, polyester acrylate resins, polyurethane acrylate resins, andepoxy acrylate resins.

The photoinitiator, more specifically, the UV initiator, is added to theUV-curable resin in a small amount, and initiates a polymerizationreaction upon receiving UV rays emitted from a UV lamp.

The photocuring reaction may be affected by the light intensity, thewavelength of the light, the irradiation time of the light, thethickness of the composition, the type of the initiator, theconcentration, and the like.

According to an embodiment, the composition for forming the adhesivelayer PSA3 includes at least one photoinitiator having a differentconcentration in the first direction D1.

Referring to FIG. 21, a photocurable composition (hereinafter, a“composition”) may include a first composition applied from the frontsurface S1 to the first point P1 and a second composition applied fromthe first point P1 to the rear surface S2.

The first composition includes a photocurable resin (hereinafter, a“resin”) and a first photoinitiator (hereinafter, an “initiator”). Asecond composition includes a resin and a second photoinitiator(hereinafter, an “initiator”). The first composition and the secondcomposition may include substantially the same resin. The firstinitiator and the second initiator initiate the polymerization reactionwith light having a first wavelength and light having a secondwavelength, respectively. The first wavelength and the second wavelengthmay be different from each other. The first initiator initiates thepolymerization reaction by the light having the first wavelength, butdoes not initiate the polymerization reaction by the light having thesecond wavelength. The second initiator initiates the polymerizationreaction by the light having the second wavelength, but does notinitiate the polymerization reaction by the light having the firstwavelength.

A short wavelength initiator initiates the polymerization reaction bylight having a short wavelength in a range from about 220 nm to about320 nm, but does not initiate the polymerization reaction by lighthaving a wavelength of about 320 nm or more. An intermediate wavelengthinitiator initiates the polymerization reaction by light having anintermediate wavelength in a range from about 260 nm to about 380 nm,but does not initiate the polymerization reaction by light having awavelength of about 380 nm or more. A long wavelength initiatorinitiates the polymerization reaction by light having a long wavelengthin a range from about 340 nm to about 440 nm, but does not initiate thepolymerization reaction by light having a wavelength of about 440 nm ormore.

The first initiator may include any one of the short wavelength, theintermediate wavelength and the long wavelength initiators, and thesecond initiator may include another of the short wavelength, theintermediate wavelength and the long wavelength initiators.

For example, an initiator having an active wavelength band of arelatively short wavelength may include, for example, IRGACURE® 184,250, 369, 500, 651, 754, 907, 1300, 2959, DAROCUR® 1173, and MBF, whilean initiator having an active wavelength band of a relatively longwavelength may include, for example, IRGACURE® 784, 819, 2022, 2100, andDAROCUR® TPO.

Referring to FIG. 21, the first initiator has a concentration of De1from the front surface S1 to the first point P1, and is not includedfrom the first point P1 to the rear surface S2. The second initiator isnot included from the front surface S1 to the first point P1, and has aconcentration of De2 from the first point P1 to the rear surface S2. De1and De2 may be substantially the same as each other or may be differentfrom each other.

Referring to FIG. 22, the first initiator has a concentration of De1 atthe front surface S1, and the concentration decreases, as closer to therear surface S2. The second initiator has a concentration of De2 at therear surface S2, and the concentration decreases, as closer to the frontsurface S1. The concentrations of De1 and De2 may be substantially thesame as each other or may be different from each other. The firstinitiator and the second initiator may each have a substantiallyconstant concentration adjacent to the front surface S1 and the rearsurface S2.

The concentration graph of FIG. 21 may correspond to a state immediatelyafter the application of the first composition and the secondcomposition, and FIG. 22 may correspond to a state in which the firstinitiator and the second initiator are each diffused beyond the firstpoint P1 after the application of the first composition and the secondcomposition.

Referring to FIGS. 21 and 22, curing of an area adjacent to the frontsurface S1 mainly affected by the first initiator, and curing of an areaadjacent to the rear surface S2 is mainly affected by the secondinitiator. Accordingly, the area adjacent to the front surface S1 may becured by irradiating the area with light having the first wavelengththat activates only the first initiator, and the area adjacent to therear surface S2 may be cured by irradiating the area with light havingthe second wavelength that activates only the second initiator. Inaddition, the curing degree of the area adjacent to the front surface S1may be determined according to intensity of the light having the firstwavelength, an irradiation time of the light, and a concentration of thefirst initiator. In addition, independently from the curing degree ofthe area adjacent to the front surface S1, the curing degree of the areaadjacent to the rear surface S2 may be determined according to intensityof the light having the second wavelength, an irradiation time of thelight, and a concentration of the second initiator. For example, theymay be cured to have a modulus or bending stiffness illustrated withreference to FIGS. 8 to 12.

Referring to FIG. 23, the composition includes a first compositionapplied from the front surface S1 to the first point P1 and a secondcomposition applied from the first point P1 to the rear surface S2.

The first composition includes a resin and a first initiator having aconcentration of De1. The second composition includes a resin and thefirst initiator having a concentration of De2. The first composition andthe second composition may include substantially the same resin. Theconcentrations of De1 and De2 of the first initiator in the first andsecond compositions are different from each other. Any one of theconcentrations of De1 and De2 may be zero.

The first initiator has a concentration of De1 from the front surface S1to the first point P1, and has a concentration of De2 from the firstpoint P1 to the rear surface S2. The first initiator may not be includedfrom the first point P1 to the rear surface S2. In contrast, the firstinitiator may not be included from the front surface S1 to the firstpoint P1.

Referring to FIG. 24, the first initiator has a concentration of De1 atthe front surface S1, and the concentration decreases, as closer to therear surface S2. Accordingly, the first initiator may have aconcentration of De2 at the rear surface S2. The first initiators mayhave a substantially constant concentration adjacent to the frontsurface S1 and rear surface S2.

The concentration graph of FIG. 23 may correspond to a state immediatelyafter the application of the first composition and the secondcomposition, and FIG. 24 may correspond to a state in which the firstinitiator is diffused beyond the first point P1 after the application ofthe first composition and the second composition.

Referring to FIGS. 23 and 24, the concentration of the first initiatorvaries along the first direction D1. Accordingly, the curing degree ofthe respective areas adjacent to the front surface S1 and the rearsurface S2 may be different depending on the concentration of the firstinitiator. Generally, part having a relatively higher concentration ofthe initiator is cured to have a relatively higher modulus or bendingstiffness. For example, it may be cured to have a modulus or bendingstiffness illustrated in FIGS. 8 to 12.

Referring to FIG. 25, the composition includes a first compositionapplied from the front surface S1 to the fifth point P5, a secondcomposition applied from the fifth point P5 to the sixth point P6, and athird composition applied from the sixth point P6 to the rear surfaceS2.

The first composition includes a resin and a first initiator. The secondcomposition includes a resin and a second initiator. The thirdcomposition includes a resin and a third initiator. The firstcomposition, the second composition and the third composition may eachinclude substantially the same resin. The first initiator, the secondinitiator, and the third initiator may have active wavelength bandsdifferent from each other.

For example, the first initiator may include any one of short,intermediate and long wavelength initiators, the second initiator mayinclude another of the short, intermediate and long wavelengthinitiators, and the third initiator may include the other of the short,intermediate and long wavelength initiators.

Alternatively, the first initiator and the third initiator may haveactive wavelength bands different from that of the second initiator, andthe first initiator and the third initiator may have substantially thesame active wavelength band. The first initiator and the third initiatormay include substantially the same material.

Referring to FIG. 25, the first initiator has a concentration of De1from the front surface S1 to the fifth point P5 and is not included inthe rest. The second initiator has a concentration of De2 from the fifthpoint P5 to the sixth point P6. and is not included in the rest. Thethird initiator has a concentration of De3 from the sixth point P6 tothe rear surface S2 and is not included in the rest. The concentrationsof De1, De2 and De3 may be substantially the same as each other or maybe different from each other. The concentrations of De1 and De3 may besubstantially the same as each other and may be different from theconcentration of De2.

Referring to FIG. 26, the first initiator has a concentration of De1 atthe front surface S1, and the concentration decreases, as closer to therear surface S2. The second initiator has a concentration of De2 at thefourth point P4, and the concentration decreases, as closer to the frontsurface S1 or the rear surface S2. The third initiator has aconcentration of De3 at the rear surface S2, and the concentrationdecreases, as closer to the front surface S1. The first initiator, thesecond initiator, and the third initiator may have a substantiallyconstant concentration adjacent to the front surface S1, the fourthpoint P4, and the rear surface S2, respectively.

The concentration graph of FIG. 25 may correspond to a state immediatelyafter the application of the first composition, the second compositionand the third composition, and FIG. 26 may correspond to a state inwhich the first composition, the second composition, and the thirdcomposition are each diffused after the application of the firstcomposition, the second composition and the third composition.

Referring to FIGS. 25 and 26, curing of an area adjacent to the frontsurface S1 is mainly affected by the first initiator, curing of an areaadjacent to the fourth point P4 is mainly affected by the secondinitiator, and curing of an area adjacent to the rear surface S2 ismainly affected by the third initiator. Accordingly, the curing degreeof the areas adjacent to the front surface S1, the fourth point P4 andthe rear surface S2 may be independently determined. For example, theymay be cured to have a modulus or bending stiffness illustrated in FIGS.14 to 16. As such, the modulus or bending stiffness may be adjustedaccording to a position in the adhesive layer by adjusting a type and/orconcentration of an initiator included in each composition.

Referring to FIG. 27, the composition includes a first compositionapplied from the front surface S1 to the fifth point P5, a secondcomposition applied from the fifth point P5 to the sixth point P6, and athird composition applied from the sixth point P6 to the rear surfaceS2.

The first composition includes a resin and a first initiator having aconcentration of De1. The second composition includes a resin and thefirst initiator having a concentration of De2. The third compositionincludes a resin and the first initiator having a concentration of De3.The first, second, and third compositions may include substantially thesame resin. The concentrations of De1 and De3 of the first initiator ofthe first and third compositions are different from the concentration ofDe2 of the first initiator of the second composition. The concentrationsof De1 and De3 of the first initiator of the first and thirdcompositions may be substantially the same as each other or differentfrom each other. The concentrations of De1 and De3 of the firstinitiator of the first and third compositions may be zero. In contrast,the concentration of De2 of the first initiator of the secondcomposition may be zero.

Referring to FIG. 27, the first initiator has a concentration of De1from the front surface S1 to the fifth point P5, has a concentration ofDe2 from the fifth point P5 to the sixth point P6, and has aconcentration of De3 from the sixth point P6 to the rear surface S2.

Referring to FIG. 28, the first initiator has a highest concentration ofDe2 at the fourth point P4, and the concentration decreases, as closerto the front surface S1 or the rear surface S2. However, embodiments arenot limited thereto, and the first initiator may have a lowestconcentration of De2 at the fourth point P4, and the concentration mayincrease, as closer to the front surface S1 or the rear surface S2.

The concentration graph of FIG. 27 may correspond to a state immediatelyafter the application of the first, second, and third compositions, andFIG. 28 may correspond to a state in which the first composition isdiffused after application of the first, second, and third compositions.

Referring to FIGS. 27 and 28, the concentration of the first initiatorvaries along the first direction D1. Accordingly, the curing degree ofthe area adjacent to the front surface S1, the fourth point P4, and therear surface S2 may be different from each other depending on theconcentration of the first initiator. For example, it may be cured tohave a modulus or bending stiffness illustrated in FIGS. 14 to 16.

FIGS. 29A to 29G are cross-sectional views illustrating an embodiment ofa method of manufacturing an adhesive layer.

Referring to FIG. 29A, a first release film 510 at which an adhesivelayer is to be formed is prepared.

Referring to FIG. 29B, a first composition 410 is applied on the firstrelease film 510. The first composition 410 may correspond to the firstcomposition applied from the front surface S1 to the first point P1,described with reference to FIG. 21.

Referring to FIG. 29C, a second composition 420 is applied on the firstcomposition 410. The second composition 420 may correspond to the secondcomposition applied from the first point P1 to the rear surface S2,described with reference to FIG. 21.

Referring to FIG. 29D, the first initiator included in the firstcomposition 410 and the second initiator included in the secondcomposition 420 are diffused such that the concentration of the firstinitiator and the second initiator varies gradually. The concentrationsof the first initiator and the second initiator may correspond to thoseillustrated in FIG. 22.

Referring to FIG. 29E, a UV lamp 610 emits a UV ray 611 to an uncuredcomposition 430. Only the first initiator initiates the polymerizationreaction by the UV ray 611 having the first wavelength. Depending on thedesired modulus and bending stiffness at the front surface S1, intensityand an irradiation time of the UV ray 611 having the first wavelengthand a concentration of the first initiator may be determined.

Referring to FIG. 29F, a UV lamp 620 emits a UV ray 621 to a partiallycured composition 440. Only the second initiator initiates thepolymerization reaction by the UV ray 621 having the second wavelength.Depending on the desired modulus and bending stiffness at the rearsurface S2, intensity and an irradiation time of the UV ray 611 havingthe first wavelength and a concentration of the second initiator may bedetermined.

Curing with UV rays having the second wavelength may be performed beforecuring with UV rays having the first wavelength, and curing with UV rayshaving the first wavelength and curing with UV rays having the secondwavelength may be simultaneously performed.

Referring to FIG. 29G, a second release film 520 is attached on a curedcomposition 450. The second release film 520 may be disposed on theuncured composition 430, and then curing with UV rays having the firstwavelength and curing with UV rays having the second wavelength may beperformed thereon. After the first release film 510 and the secondrelease film 520 are removed, the adhesive layer 450 is attached betweenthe display panel DP and the cover member CM.

FIGS. 30A to 30C are cross-sectional views illustrating anotherembodiment of a method of manufacturing an adhesive layer.

Referring to FIG. 30A, a first composition 410 is applied on a firstrelease film 510. The first composition 410 may correspond to the firstcomposition applied from the front surface S1 to the first point P1,described with reference to FIG. 21. In addition, a second composition420 is applied on a second release film 520. The second composition 420may correspond to the second composition applied from the first point P1to the rear surface S2, described with reference to FIG. 21.

Referring to FIG. 30B, the first release film 510 and the second releasefilm 520 are laminated on each other, while the first composition 410and the second composition 420 face each other.

Referring to FIG. 30C, the first initiator included in the firstcomposition 410 and the second initiator included in the secondcomposition 420 are diffused, thereby forming a composition in which theconcentration of the first initiator and the second initiator variesgradually. The concentrations of the first initiator and the secondinitiator may correspond to those illustrated in FIG. 22.

Next, as described above with reference to FIGS. 29E and 29F, curingwith the UV ray 611 having the first wavelength and curing with the UVray 621 having the second wavelength may be performed.

FIGS. 31A to 31F are cross-sectional views illustrating still anotherembodiment of a method of manufacturing an adhesive layer.

Referring to FIG. 31A, a first initiator 411 is applied on a firstrelease film 510.

Referring to FIG. 31B, a resin 412 is applied on the first initiator411.

Referring to FIG. 31C, a second initiator 421 is applied on a secondrelease film 520, and a resin 422 is applied on the second initiator421.

Referring to FIG. 31D, the first initiator 411 is diffused into theresin 412 to form a first composition 410-1, and the second initiator isalso diffused into the resin 422 to form a second composition 420-1.

Referring to FIG. 31E, the first release film 510 and the second releasefilm 520 are laminated on each other while both compositions 410-1 and420-1 face each other.

Referring to FIG. 31F, the first initiator 411 is diffused into thesecond composition 420-1 and the second initiator 421 is diffused intothe first composition 410-1, thereby forming a composition 430-1 inwhich the concentration of the first initiator and the second initiatorvaries gradually. The concentrations of the first initiator and thesecond initiator may correspond to those in FIG. 22.

Next, as described above with reference to FIGS. 29E and 29F, curingwith the UV ray 611 having the first wavelength and curing with the UVray 621 having the second wavelength may be performed.

FIGS. 32A to 32D are cross-sectional views illustrating yet anotherembodiment of a method of manufacturing an adhesive layer.

Referring to FIG. 32A, a first initiator 411 is applied on a firstrelease film 510, and a resin 412 is applied on the first initiator 411.

Referring to FIG. 32B, the first initiator 411 is diffused into theresin 412, thereby forming a composition 410-1 in which theconcentration of the first initiator varies gradually. The concentrationof the first initiator in the composition 410-1 may correspond to thatillustrated in FIG. 24.

Referring to FIG. 32C, as described above with reference to FIG. 29E,curing with a UV ray 611 having the first wavelength may be performed.

Referring to FIG. 32D, a second release film 520 is attached on a curedcomposition 440-1. The second release film 520 may be disposed on thecomposition 410-1 which is uncured, and then curing with the UV rayshaving the first wavelength may be performed thereon.

FIGS. 33A to 33E are cross-sectional views illustrating still yetanother embodiment of a method of manufacturing an adhesive layer.

Referring to FIG. 33A, a first release film 510 at which an adhesivelayer is to be formed is prepared, and a first composition 410 isapplied on the first release film 510. The first composition 410 maycorrespond to the first composition applied from the front surface S1 tothe fifth point P5, described above with reference to FIG. 25.

Referring to FIG. 33B, a second composition 420 is applied on the firstcomposition 410. The second composition 420 may correspond to the secondcomposition applied from the fifth point P5 to the sixth point P6,described with reference to FIG. 25.

Referring to FIG. 33C, a third composition 415 is applied on the secondcomposition 420. The third composition 415 may correspond to the thirdcomposition applied from the sixth point P6 to the rear surface S2,described above with reference to FIG. 25. The third composition 415 maybe substantially the same as the first composition 410.

Referring to FIG. 33D, the first initiator included in the firstcomposition 410, the second initiator included in the second composition420, and the third initiator included in the third composition 415 arediffused, thereby forming a composition 470 in which the concentrationof the first initiator, the second initiator, and the third initiatorvaries gradually in the first direction D1. The concentrations of thefirst initiator, the second initiator, and the third initiator in thecomposition 470 may correspond to those in FIG. 26.

Next, to the composition 470 which is uncured, a UV lamp 610 emits a UVray 611 having a first wavelength, a UV lamp 620 emits a UV ray 621having a second wavelength, and a UV lamp 630 emits a UV ray 631 havinga third wavelength. The first, second, and third wavelengths correspondto active wavelength bands of the first, second, and third wavelengths,respectively.

Referring to FIG. 33E, a second release film 520 is attached on a curedcomposition 480. The second release film 520 may be disposed on thecomposition 470 which is uncured, and then curing may be performedthereon.

FIGS. 34 and 35 are graphs each illustrating a concentration of aninitiator before curing an adhesive layer according to embodiments. InFIGS. 34 and 35, a vertical axis denotes a concentration of theinitiator, and a horizontal axis denotes a position in the seconddirection D2.

Referring to FIG. 34, the composition includes a first compositionapplied from the first side surface S3 to the eighth point P8, a secondcomposition applied from the eighth point P8 to the ninth point P9, anda third composition applied from the ninth point P9 to the second sidesurface S4.

The first composition includes a resin and a first initiator. The secondcomposition includes a resin and a second initiator. The thirdcomposition includes a resin and a third initiator. The firstcomposition, the second composition, and the third composition mayinclude substantially the same resin. The first initiator, the secondinitiator, and the third initiator may have different active wavelengthbands. Alternatively, the first initiator and the third initiator mayhave active wavelength bands different from the active wavelength bandof the second initiator, and the first initiator and the third initiatormay have substantially the same active wavelength band. The firstinitiator and the third initiator may include the substantially samematerial.

Referring to FIG. 34, the first initiator has a concentration of De1from the first side surface S3 to the eighth point P8 and is notincluded in the rest. The second initiator has a concentration of De2from the eighth point P8 to the ninth point P9 and is not included inthe rest. The third initiator has a concentration of De3 from the ninthpoint P9 to the second side face S4 and is not included in the rest. Theconcentrations of De1, De2 and De3 may be substantially the same as eachother or may be different from each other. The concentrations of De1 andDe3 may be substantially the same as each other and may be differentfrom the concentration of De2.

Referring to FIG. 35, the first initiator has a concentration of De1 atthe first side surface S3, and the concentration decreases, as closer tothe second side surface S2. The second initiator has a concentration ofDe2 at the seventh point P7, and the concentration decreases, as closerto the first side surface S3 or the second side surface S4. The thirdinitiator has a concentration of De3 at the second side S4, and theconcentration decreases, as closer to the first side surface S3. Thefirst initiator, the second initiator, and the third initiator may eachhave a constant concentration adjacent to the first side surface S3, theseventh point P7, and the second side surface S4.

The concentration graph of FIG. 34 may correspond to a state immediatelyafter the application of the first composition, the second compositionand the third composition, and FIG. 35 may correspond to a state inwhich the first composition, the second composition and the thirdcomposition are diffused after the application of the first composition,the second composition and the third composition.

Referring to FIGS. 34 and 35, the curing of the non-folding area NFA ismainly affected by the first initiator and the third initiator, and thecuring of the folding area FA is mainly affected by the secondinitiator. Accordingly, the curing degree of the folding area FA and thenon-folding area NFA may be determined independently. For example, itmay be cured to have a modulus or bending stiffness illustrated in FIGS.18 to 20.

FIGS. 36A to 36E are cross-sectional views illustrating yet stillanother embodiment of a method of manufacturing an adhesive layer.

Referring to FIG. 36A, a first release film 510 at which an adhesivelayer is to be formed is prepared, and a first composition 410 isapplied on the first release film 510. The first composition 410 maycorrespond to the first composition applied from the first side surfaceS3 to the eighth point P8, described above with reference to FIG. 34.

Referring to FIG. 36B, a second composition 420 is applied on the firstrelease film 510 so as to contact the first composition 410. The secondcomposition 420 may correspond to the second composition applied fromthe eighth point P8 to the ninth point P9, described above withreference to FIG. 34. An area from the eighth point P8 to the ninthpoint P9 may correspond to the folding area FA. The area from the eighthpoint P8 to the ninth point P9 may be larger than the folding area FAand may include the entire folding area FA.

Referring to FIG. 36C, a third composition 415 is applied on the firstrelease film 510 so as to contact the second composition 420. The thirdcomposition 415 may correspond to the third composition applied from theninth point P9 to the second side surface S4, described with referenceto FIG. 34.

Referring to FIG. 36D, the first initiator included in the firstcomposition 410, the second initiator included in the second composition420, and the third initiator included in the third composition 415 arediffused such that the concentration of the first initiator, the secondinitiator, and the third initiator varies gradually in the seconddirection. The concentration of the first initiator, the secondinitiator, and the third initiator may correspond to that illustrated inFIG. 35.

Next, to an uncured composition 490, a UV lamp 610 emits a UV ray 611having a first wavelength, a UV lamp 620 emits a UV ray 621 having asecond wavelength, and a UV lamp 630 emits a UV ray 631 having a thirdwavelength. The first, second, and third wavelengths correspond toactive wavelength bands of the first, second, and third initiators,respectively.

Referring to FIG. 36E, a second release film 520 is attached on a curedcomposition 495. The second release film 520 may be disposed on theuncured composition 490, and then curing may be performed thereon.

Although certain embodiments and implementations have been describedherein, other embodiments and modifications will be apparent from thisdescription. Accordingly, the inventive concepts are not limited to suchembodiments, but rather to the broader scope of the appended claims andvarious obvious modifications and equivalent arrangements as would beapparent to a person of ordinary skill in the art.

What is claimed is:
 1. A display device comprising: a display panel; acover member disposed on the display panel; and an adhesive layerdisposed between the display panel and the cover member, wherein theadhesive layer has a first surface facing the cover member and a secondsurface facing the display panel, and comprises a first area and asecond area disposed at positions different from each other in a firstdirection from the first surface toward the second surface, and whereina modulus of the first area is different from a modulus of the secondarea, wherein a bending stiffness of the first area is about 30 N·cm orhigher and about 50 N·cm or lower, and a bending stiffness of the secondarea is about 15 N·cm or higher and about 30 N·cm or lower.
 2. Thedisplay device of claim 1, wherein the adhesive layer forms a singlelayer including the first area and the second area without an interfacebetween the first surface and the second surface.
 3. The display deviceof claim 1, wherein the adhesive layer has a continuous modulus betweenthe first surface and the second surface.
 4. The display device of claim1, wherein the modulus of the first area is about 100 Kpa or higher andabout 1000 Kpa or lower, and the modulus of the second area is about 100Kpa or lower.
 5. The display device of claim 1, wherein a differencebetween the modulus of the first area and the modulus of the second areais about 100 Kpa or greater.
 6. The display device of claim 1, wherein:the first area comprises the first surface; the second area comprisesthe second surface; and the modulus of the first area is higher than themodulus of the second area.
 7. The display device of claim 1, wherein:the first area comprises the first surface; the second area comprisesthe second surface; and the modulus of the first area is lower than themodulus of the second area.
 8. The display device of claim 1, wherein:each the moduli of the first and the second areas varies gradually alongthe first direction; the first area comprises the first surface; and thesecond area comprises the second surface.
 9. The display device of claim1, wherein the adhesive layer further comprises a third area having amodulus that varies gradually along the first direction.
 10. The displaydevice of claim 9, wherein the third area has a modulus that decreasesgradually along the first direction.
 11. The display device of claim 9,wherein: the first area comprises the first surface; the second areacomprises the second surface; the third area is disposed between thefirst area and the second area; and the modulus of the first area andthe modulus of the second area are constant in the first direction. 12.The display device of claim 9, wherein the third area has a modulus thatincreases gradually along the first direction.
 13. The display device ofclaim 1, wherein the first area comprises a third area having a modulusthat decreases gradually along the first direction, and the second areacomprises a fourth area having a modulus that increases gradually alongthe first direction.
 14. The display device of claim 13, wherein thefirst area comprises the first surface, and the second area comprisesthe second surface.
 15. The display device of claim 13, wherein thefirst area comprises the second surface, and the second area comprisesthe first surface.
 16. The display device of claim 1, wherein theadhesive layer further comprises a third area disposed between the firstarea and the second area, and each of the modulus of the first area andthe modulus of the second area is higher than a modulus of the thirdarea.
 17. The display device of claim 1, wherein the adhesive layerfurther comprises a third area disposed between the first area and thesecond area, and each of the modulus of the first area and the modulusof the second area is lower than a modulus of the third area.
 18. Thedisplay device of claim 1, wherein the display device is foldable orrollable.
 19. A display device comprising: a display panel; a covermember disposed on the display panel; and a single adhesive layercomprising a first surface facing the cover member and a second surfacefacing the display panel without an interface between the first surfaceand the second surface, the single adhesive layer being disposed betweenthe display panel and the cover member, wherein a modulus of the firstsurface is higher than a modulus of the second surface, wherein amaximum value of a bending stiffness of the adhesive layer is about 30N·cm or higher and about 50 N·cm or lower, and a minimum value of thebending stiffness of the adhesive film is about 15 N·cm or higher andabout 30 N·cm or lower.
 20. The display device of claim 19, wherein adifference between the modulus of the first surface and the modulus ofthe second surface is about 100 Kpa or greater.
 21. A display devicecomprising: a display panel; a cover member disposed on the displaypanel; and an adhesive layer disposed between the display panel and thecover member, wherein the adhesive layer comprises non-folding areas anda folding area disposed between the non-folding areas, and wherein amodulus of the folding area is greater than a modulus of the non-foldingarea.
 22. The display device of claim 21, wherein the modulus of thefolding area is about 100 Kpa or higher and about 1000 Kpa or lower, andthe modulus of the non-folding area is about 100 Kpa or lower.
 23. Thedisplay device of claim 21, wherein a difference between the modulus ofthe folding area and the modulus of the non-folding area is about 100Kpa or greater.
 24. An adhesive film for a display device, the adhesivefilm having a first surface and a second surface opposing the firstsurface, and comprising a first area and a second area disposed atpositions different from each other in a thickness direction from thefirst surface toward the second surface, wherein a modulus of the firstarea is different from a modulus of the second area, wherein a bendingstiffness of the first area is about 30 N·cm or higher and about 50N·cm, or lower, and a bending stiffness of the second area is about 15N·cm or higher and about 30 N·cm or lower.
 25. The adhesive film ofclaim 24, wherein the adhesive film forms a single layer including thefirst area and the second area without an interface between the firstsurface and the second surface.
 26. The adhesive film of claim 24,wherein a maximum value of a modulus of the adhesive film is about 100Kpa or higher and about 1000 Kpa or lower, and a minimum value of themodulus of the adhesive film is about 100 Kpa or lower.
 27. The adhesivefilm of claim 24, wherein a deviation of a modulus of the adhesive filmin the thickness direction is about 100 Kpa or greater.
 28. The adhesivefilm of claim 24, wherein a modulus of the adhesive film increasesgradually along the thickness direction.
 29. The adhesive film of claim24, wherein the first area comprises a third area having a modulus thatdecreases gradually along the thickness direction, and the second areacomprises a fourth area having a modulus that increases gradually alongthe thickness direction.
 30. The adhesive film of claim 24, furthercomprising a third area disposed between the first area and the secondarea, wherein each of the modulus of the first area and the modulus ofthe second area is higher than a modulus of the third area.
 31. Theadhesive film of claim 24, further comprising a third area disposedbetween the first area and the second area, wherein each of the modulusof the first area and the modulus of the second area is lower than amodulus of the third area.
 32. An adhesive film for a display device,the adhesive film having a first surface and a second surface opposingthe first surface without an interface between the first surface and thesecond surface, wherein a modulus of the first surface is higher than amodulus of the second surface, wherein a bending stiffness of the firstsurface of the adhesive film is between about 30 N cm and about 50 N cm,and a bending stiffness of the second surface of the adhesive film isbetween about 15 N cm and about 30 N cm.